Hydrodynamic chronoamperometry for probing kinetics of anaerobic microbial metabolism – case study of Faecalibacterium prausnitzii

Abstract

Monitoring in vitro the metabolic activity of microorganisms aids bioprocesses and enables better understanding of microbial metabolism. Redox mediators can be used for this purpose via different electrochemical techniques that are either complex or only provide non-continuous data. Hydrodynamic chronoamperometry using a rotating disc electrode (RDE) can alleviate these issues but was seldom used and is poorly characterized. The kinetics of Faecalibacterium prausnitzii A2-165, a beneficial gut microbe, were determined using a RDE with riboflavin as redox probe. This butyrate producer anaerobically ferments glucose and reduces riboflavin whose continuous monitoring on a RDE provided highly accurate kinetic measurements of its metabolism, even at low cell densities. The metabolic reaction rate increased linearly over a broad range of cell concentrations (9 × 104 to 5 × 107 cells.mL−1). Apparent Michaelis-Menten kinetics was observed with respect to riboflavin (KM = 6 μM; kcat = 5.3×105 s−1, at 37 °C) and glucose (KM = 6 μM; kcat = 2.4 × 105 s−1). The short temporal resolution allows continuous monitoring of fast cellular events such as kinetics inhibition with butyrate. Furthermore, we detected for the first time riboflavin reduction by another potential probiotic, Butyricicoccus pullicaecorum. The ability of the RDE for fast, accurate, simple and continuous measurements makes it an ad hoc tool for assessing bioprocesses at high resolution.

A Novel Shewanella Isolate Enhances Corrosion by Using Metallic Iron as the Electron Donor with Fumarate as the Electron Acceptor

“…S5B). This further confirmed that strain 4t3-1-2LB did not excrete dissolved redox mediators to the liquid phase at a detectable concentration in our experiments (47).…”

The electron donating capacity of biochar is dramatically underestimated

“…The presence of char did not modify the sigmoidal shape of the CV nor the difference between the anodic and cathodic plateaus currents. This proves that the total amount of dissolved [ferricyanide + ferrocyanide] stayed constant over the experiment 29 . In particular, it demonstrates the absence of notable adsorption of these redox species on the char surface.…”

“…Regarding the limited amount of data related to EEC values of biochars as well as some apparent discrepancies, we aimed here to quantify the amount of electrons that can be accepted or donated by wood-based chars pyrolyzed at different HTTs. To do so, we took advantages of highly accurate hydrodynamic electrochemical techniques with rotating disc electrodes (RDE) in order to monitor the redox state of oxidative or reductive solutions reacting with the biochars 29 . After validation of the method, we compared our values with previously published data obtained with similar biochars (feedstock from identical genus – Pinus – and identical HTTs).…”

Electrobioremediation of oil spills

“…Further research is required to determine if the use of electrodes for sulfide removal (Figure 4 The current into the circuit should therefore be proportional to the rate at which the electrons are transferred to the electrode by the oxidation reaction (for the anodic process), or diverted by the reduction reaction (for the cathodic process). Hypothesizing that only one metabolic process is occurring on the electrode surface, the produced current can thus be used as a real time parameter to quantify the rate of a specific metabolic process (Prévoteau et al, 2015) or a measure of the substrate concentration available for microbial degradation. Previous studies demonstrated that the current production can be correlated to COD and BOD and that a relationship can be described by Monod type kinetics (Kim et al, 2003;Kumlanghan et al, 2007;Min and Logan, 2004).…”